Coiled tubing operations in oil and gas wells generally involve delivering by large pumping units pressurized fluid mixtures downhole through a coiled tubing string. Chemical additives and lubricants are commonly added to fluid mixtures as an integral step for performing efficient coiled tubing operations. Chemical additives and lubricants have generally been hand mixed by personnel on the side in small batches and poured through an open top of a mixing tank associated with the pumping unit, or mixed in another unit and delivered to the pumping unit. However, these mixtures are generally inadequately mixed and unstable due to air in the mixture. Moreover, water is poured into the mixture through an open top of a mixing tank causing the water to splash and bubble inside the tank. The air pockets created result in an improper mixture and are detrimental to coiled tubing operations when forced downhole. Previous mixing tanks have also generally been inadequate for running specialized fluid mixtures downhole, such as gel sweeps. What is needed then is an improved chemical mixing and pumping unit for oilfield operations.
In one aspect, embodiments disclosed herein relate to a chemical mixing and pumping unit for oilfield operations including at least one mixing tank onboard the chemical mixing and pumping unit. The mixing tank includes one or more mixing paddles within the mixing tank capable of agitating liquids therein, one or more water inlets capable of introducing water into the mixing tank and directing water flow toward the one or more mixing paddles, and one or more chemical inlets capable of introducing one or more chemicals into the mixing tank. The chemical mixing and pumping unit further includes one or more storage tanks capable of storing chemicals onboard the chemical mixing and pumping unit, and one or more pumps corresponding to the individual storage tanks capable of delivering chemicals from the storage tanks to the one or more chemical inlets in the at least one mixing tank.
In another aspect, embodiments disclosed herein relate to a mixing tank disposed onboard a unit for coiled tubing oilfield operations, the mixing tank including a mixing paddle within the mixing tank capable of agitating liquids therein, a water inlet capable of introducing water into the mixing tank and directing water flow toward the mixing paddle, and one or more chemical inlets capable of introducing one or more chemicals from chemical storage units into the mixing tank.
In yet another aspect, embodiments disclosed herein relate to a method of mixing liquids in a mixing tank prior to pumping a liquid mixture downhole. The method includes inputting one or more chemicals into the mixing tank through one or more corresponding chemical inlets, inputting water into the mixing tank through a water inlet at the bottom of the mixing tank and directing the water towards a mixing paddle within the mixing tank, and rotating the mixing paddle in a direction opposite that of the water stream directed towards the mixing paddle, thereby agitating and mixing liquids within the mixing tank.